Acoustic Wave Structure With Reinforced Through-Hole Crack Control
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Solution Overview
Problem
Acoustic wave devices with through-holes in piezoelectric layers are prone to crack generation due to displacement interference, which affects the device's performance and reliability.
Innovation Solution
Incorporating a reinforcement film between the through-holes and space portions in the piezoelectric layer, and extending passages to reduce stress concentration and prevent crack formation, while ensuring the through-holes do not overlap with functional electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a through-hole is provided in the piezoelectric layer for etching a sacrificial layer, then the space portion between the support substrate and the piezoelectric layer can be formed, but cracks starting from the through-hole may be generated in the piezoelectric layer due to displacement interference
Solution Approach 1:
An extended passage is introduced as an intermediary structure between the through-hole and the space portion. The extended passage extends farther toward the outer side than the edge of the space portion in a direction intersecting the thickness direction, serving as a stress-relief zone that prevents crack propagation from the through-hole to the functional electrode region while maintaining the necessary space for sacrificial layer removal
Solution Approach 2:
The extended passage extends in a direction intersecting the thickness direction (horizontal extension beyond the space portion edge), creating an additional dimensional buffer zone. This dimensional extension allows the through-hole to communicate with the space portion without direct vertical alignment, reducing stress concentration on the piezoelectric layer
2Reliability
If the through-hole is positioned to not overlap the functional electrode in plan view, then crack generation is reduced, but the device area and complexity increase
Solution Approach 1:
The extended passage is merged with the through-hole structure to form an integrated communication path. The extended passage and through-hole together create a unified structure that achieves crack prevention while maintaining compact device layout, avoiding the need for separate protective structures
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces or prevents crack generation in the piezoelectric layer, enhancing the device's stability and resonance characteristics without compromising miniaturization or increasing propagation loss.
Implementation Method 1
a piezoelectric layer provided in a first direction of the support, the first direction being a thickness direction of the support substrate
Implementation Method 2
at least one functional electrode provided in the first direction of the piezoelectric layer
Data Source
AI summary
An acoustic wave device includes a support including a support substrate, a piezoelectric layer on the support in a first direction, a functional electrode on the piezoelectric layer, and a reinforcement film on the piezoelectric layer. The support includes a space portion that opens on a side of the piezoelectric layer, and an extended passage extending farther toward an outer side than an edge of the space portion in a second direction intersecting the first direction. A through-hole is provided at a position not overlapping the functional electrode in plan view in the first direction, communicates with the extended passage, and penetrates the piezoelectric layer. The reinforcement film is provided in a region between the through-hole and the space portion and overlaps at least a portion of a region where the piezoelectric layer and the extended passage overlap each other in the plan view.